Alternating-current motor.



PATENTED NOV. 12, 1907. R. LUNDELL.

ALTERNATING CURRENT MOTOR.

APPLICATION FILED NOV. 27, 1905.

' 2 sums-sum 1.

PATENTED NOV. 12, 1907. R. LUNDELL.

ALTERNAT ING CURRENT MOTOR.

APPLICATION FILED NOV. 27, 1905.

2 SHEETS-SHEET 2.

ROBERT LUNDELL, OF NEW YORK, N. Y.

sn'rnnnarms-cnnnnnr Moron.

Specification of Letters Patent.

Patented Nov. 12, 1907.

pplication fi v r 27.1905. semi No. 289,178-

To all whom it my 001m."

Be it known that I, Rosln'r Lnnnmm, a citizenof the United States, residing in New Yorkfborough of Manhattan, county and State of New York, have made a new and useful Invention in Alternating-Current Motors, of which the following is a specification.

The present invention relates to that class of alternating current motors which are furnished with a commutator and which may be operated from a single phase or two-wire circuit.

It relates particularly to a type of motor described by me in a prior United States patent No 782,863, granted February 21st, 1905. In this type of motor the armature or rotor is caused to rotate in its field magnet or stator by the torque effects of short circuited currents in certain groups of armature coils, combined with the torque effects of other currents from an outside source of alternating current supply, which are caused to flow through the remaining groups of armature coils. In the above-mentioned patent I have also shown means for reversing the direction of rotation by shifting the brushes from one position to another.

The objects of the present invention are-First, to provide more convenient means than those described in the above-mentioned patent for reversing the direc tion of rotation. Second, to increase the efliciency of the apparatus by combining a. symmetrically distributcd stator winding with a controller connected to various points of the stator winding for the purpose of overcoming the self-induction of the rotor winding at the highest speeds of the rotor.

Referring now to the drawings, Figure 1 represents diagrammatically an alternating current motor of the type referred to, said motor being connected to a pair of current mains through a speed regulating and pole changing switch or controller shown to the right of the figure. Fig. 2 represents the same apparatus, the chief difference being that the direction of rotation has been reversed. Fig. 3 shows a portion 0f--Fig. 2 and illustrates a different arrangement of short-circuiting the armature coils. Fig. 4 illustrates a modification of the manner in which the outside currents may be introduced into the rotor.

Referring now to Fig. 1 in detail, a rpresents the The operation of this motor will best he understood by following the currents as they flow through the varioue circuits of the apparatus-at one particular moment. The arrows shown in full lir es will indicate the direction of the primary currents and the dotted arrows will indicate the direction of the induced or the short-circuited currents. Starting then at the supply wire 11', the current flows to the stationary Contact 1 of the controller, through the regulating resistance 12 to contact 4 and to the stator terminal 14. At this point the current divides itself in the stator winding or the circuit 14 to 17, causing polarities N, S, as clearly shown on the drawing. From the stator terminal 17 the current flows to other stationary controller contar-ts '7 and 8, then to brush 18 at which it again divides itself in the two-circuit rotor winding, as clearly shown by the arrows drawn in full. From the other brush 19 the current finally flows to stationary contact 9 and to the other supply wire 10. ln the portions of the rotor winding which are short-circuited by the wide brushes, it will be found that the induced or the short circuitcd currents will flow as indicated by the dotted arrowsv The combined polarities from the primary and the induced currents will consequently be located about as indicated by letters N, S, on the rotor and the direction of rotation will "be opposite to that of the hands of t clock. At the nextmoment when the currents are reversed the polarities will also'be reversed and the direction of rotation remains as before Attention is now called to the movable controller contacts 20, 21 and 22, also to the four terminals 14, 15, 16 and 17 of. the stator winding. Four positions of the left hand movable contacts of the controller are indicated in 1 by the fine'broken lines drawn across the contacts. The first position puts both of the resistances 12 and 13 in series with the'rnotor. The second position (the one shown in Fig. 1) cuts out the resistance 13 andth'e'third position cuts out both of the v resistances. The fourth. and last position causes the terminals 15 and 16 of the stator winding to become connected by the movable contact 21 engaging wit the stationary controller contacts 5 and 6. In other words, two equi-potential points 15 and 16 in the stator winding 14 to 17 have now become connected or shortcircuited. These points are at 90 electrical degrees from the terminals 14 and 17. The effect of this shortcircuit is that the rotor flux, which is 90 electrical degrees from the stator flux and which increases the selfinduction of the rotor winding, has practically become nullified by the opposing secondary currents in the circuit 15 to 16 of the stator winding. The last position i versal of the direction of rotation. This has been ac-.

coinplished by a change in the connections on the controller, due to the righthand movable contacts being made to engage withthe stationary controller contacts. Following the current fiow at one particular moment same as in Fig. lp'we find that the current now enters the stator winding at terminal 15 and that it leaves the stator winding at 16. In other words, the field cir cuit has been shifted by 90 electrical degrees, thatis, from circuit 14 to 17 Fig. 1 to the circuit 15 to 16 in Fig.2. Following the current flowinto the rotor we find that the current enters by brush 18 or same as before. This gives to the primary currents in the rotor the same direction as before. The induced or the short-circu'ited currents in the rotor have, however, become reversed, owing to the shifting of the polarities N, S in the stator. These polarities have been shifted by 90 electrical degrees in a right hand direction, whereas the polarities of the rotor have been shifted by the same angle in a left hand direction, as clearly shown on the drawing. It is evident that the motor now turns in the same direction as the hands of a clock. The four positions of the right hand movable contacts of the controller cause the motor to operate prec sely as described in connection with the left hand contacts, the only difference being that the rotor revolvesin the opposite direction. The last position causes the stator terminals 14 and 17 to become connected together instead of the terminals 15 and 16 in Fig. 1, the result under the new conditions being th same as described above.

Attention is now called to Fig. 3 oi the drawings. This figure (as far as shown) is similar to Fig. 2, the only difference being that a pair of brushes 26 and '27, instead of the wide brush 18, are employed to short-circuit the corresponding part of the rotor. The rotor may be short-circuited in this manner, though the commutation will not'be as perfect as when the wide brush is employed. It will be seen that the current reverses direction in the rotor coils immediately under the brush 26, vcrymuch the same as in a direct current motor. Additional difliculties in'rega'rd to sparking will, however, be met with on account of the distributed stator winding, whichmak'es a smallair-gap under the com:

mutated coil a matter of necessity. It will consequcntly be understood that there will be sparking at the leaving edge '0; brush '26 unless theinductive voltage of the individual rotor coils is exceptionally low. iiliining in the other direction sparking would occur at thileaving edge of brush 27. Looking back at iln- Willi brush 18 in Fig. 2, we find that this brush has no loaving edge except at a point where there is no reversal of current in the rotor coils. If the stator and the rotor windings are so proportioned with relation to one another, that the primary and the short-circuited currents in the rotor coils are about alike in amperes, it follows that there can be no sparking when thw'wide brushes shown in Figs. 1 and 2am used. It is also pos sible to obtain excellent results as regards non-sparking by introducing into the rotor winding between the wide brushes a secondary current from a transformer. As there is no reversal of polarities of the brushes for a reversal of direction of rotation this modification becomes quite simple. Such an'arrangement is clearly illus trated in Fig. 4, which figure is similar to Fig. l, tho only difference being the addition of the transformer t.

It should be pointed out that the stator winding should be of sufficient cross-section to take care of the extra duty at the fourth positions of the controller, that is, it should be heavy enough to take care of the secondary currents which will flow at 90 electrical degrees to the primary currents of e rcitation. The core section of the stator should also be considerably greater than that of the rotor in order to keep the core losses within proper limits. It will be understood that as the rotor approaches synchronous. speed the core losses in the rotor will be reduced to a minimum.

Having thus described my invention what I claim and for introducing outside curi'ents into the other rotor.

coils not short-circuited; in combination with means for shifting the polarities of the stator, for the purpose of reversing the direction of rotation, substantially as described.

2. An alternating current motor comprising a stator connected to a source 'of alternating current supply, a rotor having coils connected to a'commutator; in combination with means for sbort-circuiting certain groups of rotor coils located at an angle of about forty-live electrical degrees to the stator-field, and additional means for shift- 3. An alternating current motor comprising a statorhaving a distributed energizing Windingya rotor having coils connected to a, commutator, wide brushes extending about 90 electrical degrees for sliort-cii'cuitim certain groups of rotor coils at an angle of about forty-five electrical degrees to the stator-field and for introducing outside currents into the other rotor coils not shortcircuited in combination with a controller having circuit connections leading to points'or terminals in the distributed stator winding located at about 90'electrica1 degrees from each other and menus for shifting the p arities of the stator, substantially as described I 4 An alternating current motor comprising a stator having an energizing winding, a rotor having coils connected to a commutator, stationary brushes upon the com mutator for sl1ort-circuiting certain groups of rotor coils at an angle of about forty-live electrical degrees to the stator-field and for introducing outside currents into the other rotor coils not slioi't-circuited; in combination with means on the stator for nullifying the rotor-flux and the self-induction of the rotor, add additional means for the commutator for short-circuiting certain groups of rotor coils and for introducing outside currents into the other rotor coils not short-circnited, means (or shitting the polarities ot the stator and additional means tor overcoming the self-induction o! the rotor, substantially as described.

6. An alternating current motor comprising the combination or a stator having a distributed energizing .winding, a rotor having coils connected 'to a commutaton brushes upon the commutator tor short-circuiting certain of the currents utilized to propel the rotor and for introducing into the rotor other propelling currents ,iroman outside source oi supply, and meanstor short-circuiting equipotentlal points in the stator winding, for the'purpose or nullitying the rotor-flux and the self-induction of the rotor, substantially as described. j

7.' An alternating current motor comprising the combi-- nati ot-a stator having a distributed energizing winding, a rot having coils connected .to a commutator, brushes upon the commutator tor short-clrcuiting certain groups or rotor coils and for introducingoutside currents into theother rotor coils not short-circulted, a starting switch' or controller having circuit connections to the motor and to a source of alternating current supply, and means on the controller for connecting together two equipotentlal points in the stator winding, substantially as described.

8. An, alternating currentmotor having a rotor which is propelled by the combined eilects or shortcircuited induced currents and currents from an outside source of 'supply and a stator having a distributed winding with two sets of terminals located 90 electrical degrees apart; in combination with means for introducing outside currents into the stator winding through one of said terminals and additionaimeans tor short-circuitlng the other set of terminals at will, substantially as described.

9. An alternating current commutator motor provil degrees and arranged to short-circuit certain or the currents utilized to propel the rotor and also to introduce into the rotor other propelling currents from an outside source of supply; in combination with a stator winding provided with means for shifting the polarities o! the stator and additional means for overcoming the self-induction or the rotor, substantially as described.

v with wide brushes extending approximately 90 electrical in testimony whereof I have signed my name to this 7 specification in the presence of two subscribing witnesses.

' ROBERT LUNDELL.

Witnesses:

mums,

WE? 'KIATING. 

